It is likely an errant Palestinian rocket, not an Israeli air strike, killed the baby of a BBC picture editor during fighting in Gaza last November, a UN report has indicated, challenging the widely believed story behind an image that became a symbol of what Palestinians said was Israeli aggression.

Now a report from the UN office of the high commissioner for human rights (OHCHR) says the baby was "killed by what appeared to be a Palestinian rocket that fell short of Israel".

Gaza's rulers, the militant Islamic group Hamas, whose fighters fired most of the rockets into Israel during the conflict, had no response on Monday.

BBC officials declined to comment, and Jihad Misharawi said he could not discuss the issue. An Israeli military spokesman said it could not confirm or deny whether it hit the Misharawi house.

Matthias Behnke, head of the OHCHR in the Palestinian territories, said he could not "unequivocally conclude" that the death was caused by an errantly fired Palestinian rocket. He said information gathered from witnesses led the office to report that "it appeared to be attributable to a Palestinian rocket".

He said Palestinian militants were firing rockets at Israel not far from the Misharawi home. Behnke said the area was targeted by Israeli air strikes, but the salvo that hit the Misharawi home was "markedly different".

He said there was no significant damage to the house – unusual for an Israeli strike – and witnesses reported that a fireball struck the roof of the house, which might have been part of a homemade rocket. Behnke said the type of injuries sustained by Misharawi family members were consistent with rocket shrapnel.

The Gaza-based Palestinian Centre for Human Rights (PCHR) said it still held Israel responsible for Omar's death.

The PCHR has condemned Hamas fighters and other militants in the past for errantly-fired rockets that have killed Palestinians, including during the November clash.

A researcher said the group interviewed family members, neighbours and security officials before it concluded that an Israeli strike killed the baby. She requested anonymity because she was not authorised to speak to reporters.

The baby was killed hours after the eruption of fighting following the killing of a top Hamas militant leader in an Israeli air strike, in response to sustained rocket fire from Palestinian militants in Gaza.

During the eight-day conflict about 160 Palestinians and six Israelis were killed.

The UN report did not name the Misharawi family in its one-sentence statement about the incident. Behnke said the report referred to the incident.

The report discussed the incident in the context of Palestinian militants disregarding civilians, both by firing rockets from crowded Palestinian areas and by aiming them indiscriminately into Israel.

In the same report the authors also criticised Israel for appearing to disregard civilians while pursuing militants and military targets, and for targeting civilian sites, such as hospitals, bridges and media offices.

Among many cases, they noted an 84-year-old man and his 14-year-old granddaughter were killed by an Israeli military strike on 21 November while they were in their olive orchard on Gaza's eastern border. They also cited an Israeli air strike on a crowded Gaza City neighbourhood that killed 12 people, including five children and four women.